Vitamin B12 (Cobalamin)

• Chemical Properties
   
  Cobalamin has a complex molecular structure, with the chemical formula C63​H88​CoN14​O14​P. It is relatively stable to heat but sensitive to strong acids, bases, and light. Vitamin B12 requires a special protein called intrinsic factor (secreted by the stomach lining) to be absorbed in the small intestine; without intrinsic factor, even high dietary intake may lead to deficiency.
• Food Sources
   
  Vitamin B12 is almost exclusively found in animal-derived foods, as plants do not produce it. Rich sources include liver, shellfish (such as clams and oysters), fish, meat, eggs, and dairy products. Vegans and vegetarians who avoid all animal products are at high risk of deficiency and often need to take fortified foods or supplements.

Physiological Functions

1. Hematopoiesis (Blood Cell Formation)

    

   Vitamin B12 works synergistically with folate to support the synthesis of DNA in rapidly dividing cells, especially red blood cells. It helps convert homocysteine to methionine and maintains the normal maturation of red blood cells. Deficiency can lead to megaloblastic anemia, characterized by large, immature red blood cells that cannot function properly.
    
2. Neurological System Health

    

   This vitamin is critical for maintaining the integrity of the myelin sheath—a protective layer that surrounds nerve fibers and ensures efficient transmission of nerve signals. A lack of vitamin B12 can damage the myelin sheath, leading to neurological symptoms such as numbness and tingling in the hands and feet, difficulty walking, memory loss, and even cognitive decline in severe cases.
    
3. Homocysteine Regulation

    

   Vitamin B12, along with folate and vitamin B6, helps break down homocysteine in the blood. Elevated homocysteine levels are associated with an increased risk of cardiovascular diseases, such as heart attacks and strokes; adequate B12 intake helps keep homocysteine levels within a healthy range.
    

Deficiency and Toxicity

• Deficiency Symptoms
   
  Mild deficiency may have no obvious symptoms, but long-term deficiency can cause megaloblastic anemia, fatigue, weakness, pale skin, and shortness of breath. Neurological symptoms may include peripheral neuropathy, balance problems, and mood changes. Deficiency is common in the elderly (due to reduced stomach acid and intrinsic factor secretion), vegans/vegetarians, and people with gastrointestinal disorders (such as celiac disease or Crohn’s disease).
• Toxicity
   
  Vitamin B12 has extremely low toxicity. Since it is water-soluble, excess amounts are excreted through urine rather than stored in the body. No serious adverse effects have been reported with high-dose oral supplementation, even at levels far exceeding the recommended intake.

Recommended Intake